Electrolytic recording paper containing a sequestering agent



Ueied Stat s Paten Qflie ELECTROLYTIC RECORDING PAPER CONTAIN- v ING ASEQUESTERING AGENT Robert S. Ives, Lexington, Mass., assignor to.

Milton Alden, Needham, Mass. No-Drawing. Filed June '11, 1963-, Ser. No.286,951 Claims. (Cl. 204-2) ABSTRACT OF THE DISCLOSURE a'record' ofimproved definition.

Electrolytic recording. bypassing a modulated electric curte'nt throughan electrochemical recording paper to produce markson the paper inaccordance with the cur-.

rent is well-known in the facsimile art. One type of paper utilized insuch' recording has been impregnated with a Water solution'containing anelectrolyte and an organic lake-former which combines withelectrode'metal ions to form a colored lake on the paper. Theserecording papers have been used commercially but have given rise to anumber of problems and limitations. Such papers after impregnationandparticularly after recording, have not been as? stable in, storageasis desirable and the definition of the record. .onsuch paper has beenlimited. This limited definitionis .due, partto the fact that thebackground of the record. tends. to discolor. with time and also tothefact that the recording marks have tendency to trail behind theelectrodeafter the current has stopped and to bleed later ally on'thepaper from the point of recording The*principal' pbjct of-- thisinvention'is to provide electrolytic recording material of the abovetype which is will provide a record more stable in storage and whichwith improved definition.

In accordance with this invention, the improved electrolytic recordingmaterial, for recording with a lake-forming metal electrode, comprises asupport impregnated with a water solution containing an organiclake-former, an electrolyte, and a chelating or sequestering agent, saidagent retaining stray recording metal ions in colorless form atnon-recording parts of the support. Amino carboxylic acid sequesteringagents and particularly amino polycarboxylic acids are preferred.Suitable materials include water-soluble salts ofethylenediaminetetraacetic acid (EDTA), and ofN-hydroxyethylethylenediaminetriacetic acid.

It is believed that the discoloration of the background of the recordedmaterial is to a substantial degree caused by small amounts of metallake-forming ions which either migrate in a record or are deposited innon-recording portions of the record as it moves between the electrodes.Similarly, it is believed that the trailing of the mark behind theelectrode after the recording current has ceased is due to small amountsof the metal ions combining to form a lake either by migration to thesupport or by mechanical transfer from the record to the electrode andback again to the support. Such trailing is particularly noticeable withhighly sensitive organic lake-formers. Both phenomena are substantiallyreduced with corresponding improvement in the record by the inclusion ofchelates according to this invention which complex with such stray metallakeforming ions to form colorless complexes at non-recording points ofthe record.

3,409,516 Peter en 5.1 96 8 .This invention may be better understoodbyire ference jto the following examples:

Example 1 Methylene disalicylic acid (MDA) 9 Potassium nitrate a I "9Sodium hydroxide L 2125 Versenol 120 (0.5%) 0.6

Water to make 100 cc.

Versenol 120 is the trademark of the Dow-Chemical Co. for a concentratedwater solution of the trisodium salt ofN-hydroxyethylethylenediaminetriacetic acid. 7

'- Example2 t Grams MDA 9 K C1 I I l 9 NaOH t v 2.25' Sequestrene 30A0.6.-

Water to make 100cc.

Sequestrene 30A is the trade name of the Geigy Co. for a 39% aqueoussolution of tetrasodium ethylenediaminetetraacetate.

Example 3 Grams MDA 9 KCI s 9, NaOH 2.25 Cheelox B14 Water to make 100cc.

Cheelox B-l4 is a trade name of the AntaraChemical Co. for a 41% aqueoussolution of amixture of soluble salts of amino carboxylic acids.

Example 4 V Grams Tannic acid 140 NaCl 120 Se'questrene Na- -2 1.25Water to make 2 pints.

- Sequestrene Na-2 is the trademark for a solution-of salts of aminopolycarboxylic acids by the Alrose Chemical Co.

Nullapon Fe-12 is a trademark of the General Dyestuff Corp. for aminopolycarboxylic acid salt solutions.

Example 6 Grams Protocatechuic acid 150 KNO 800 Thiourea Permakleer OH10.5

Water to make 2 gal.

1 Permakleer OH is the trade name for amino polycarboxylic :cidchelatlng agent solutions made by the Refined Products orp.

In the above examples the MDA, tannic acid, catechol and pyrocatecholare all organic lake-formers which combine with the metal electrode ionsto form a colored lake.

The potassium chloride, and sodium chloride are electro- I lytes. Othersuitable electrolytes include the chlorides, bromides and nitrates ofthe alkali metals. Other suitable organic materials which form insolublelakes with the metal ions of the electrode can be used. Suitableelectrode metals include chromium, copper, nickel and, preferably,

ll'OIl.

In the above examples the Versenol 120, Sequestrene 30A, Cheelox B-14,Sequestrene 'Na2, Nullapon Pe-12, and Perma Kleer OH are all chelates ofthe amino carboxylic acid type. Other amino carboxylic acids which maybe used include di (hydroxyethyl) glycine anddiethylenetriaminepentaacetic acid which latter compound is an effectivechelate in both alkaline and acid solutions. The di (hydroxyethyl)glycine which is an amino monooarboxylic acid is less effective than theamino polycarboxylic acid chelates. The chelates according to thisinvention are preferably used in amounts which may vary from about 0.05%to about 1.0% pure chelate by weight of the total impregnating solution.

A support, preferably paper, is impregnated with any of theabovesolutions by passing'it through a bath of the solution. Pressurerolls can be employed to remove excess. Recording paper having 40% byweight moisture is suitable. Treated paper is preferably stored insealed containers until used.

It should be understood that this disclosure is for the purpose ofillustration only and that the invention includes all equivalents andmodifications falling within the scope of the appended claims.

I claim:

1. In an electrolytic facsimile recording medium for recording solely bypassing a modulated electric current therethrough to form a' coloredmark with an organic marking compound contained therein, said mediumconsisting of a support impregnated with an electrolytically conductivesolution consisting of an electrolyte and an organic marking compoundproducing color by chemical combination with metal electrode ions, theimprovement which comprises including in said solution an aminopolycarboxylic sequestering agent for said electrode metal ions in anamount sufiicient to improve definition by complexing in colorless formrecording metal electrode ions in non-recording parts of the support.

2. A recording medium according to claim 1 wherein said sequesteringagent comprises from about 0.05 to about 1.0 percent by weight of saidsolution.

3. Electrolytic recording material according to claim 1 wherein saidsequestering agent comprises a water soluble salt of ethylenediaminepolyacetic acid.

4. Electrolytic recording material according to claim 1 wherein saidsequestering agent comprises a water soluble salt ofethylenediaminetetraacetic acid.

5. Electrolytic recording material according to claim 1 wherein saidsequestering agentcomprises a Water soluble salt ofN-hydroxyethylethylenediaminetriacetic acid.

6. A recording medium according to claim 1 wherein said marking compoundis selected from the group consisting of methylene disalicylic acid,tannic acid, catechol and protocatechuric acid.

7. A recording medium according to claim 6 wherein said metal electrodeions comprise iron.

8. A recording medium according to claim 7 wherein said sequesteringagent is selected from the group consisting of water soluble salts ofEDTA, N-hydroxyethylethylenediaminetriacetic acid, di(hydroxyethyl)glycine and diethylenetriaminepentaacetic acid.

9. Electrolytic recording material according to claim 1 which comprisesa support impregnated with a water solution containing an electrolyte,methylene disalicylic acid, and 'a sequestering agent selected from thegroup which consists of soluble salts ofN-hydroxyethylenediaminetriacetic acid and ethylenediamine tetraaceticacid.

10. Electrolytic recording material according to claim 1 which comprisesa support impregnated with a water solution containing an electrolyte, apolyhydroxy phenol, and a sequestering agent selected from the groupconsisting of soluble salts of N-hydroxyethylenediaminetriacetic acidand ethylenediaminetetraacetic acid.

References Cited UNITED STATES PATENTS 2,949,409 8/ 1960 Richards 20423,108,050 10/1963 Mandrel et a1 204'2 3,113,910 12/1963 Hepher 20423,142,562 7/1964 Blake 204-2 3,165,458 1/1965 Harriman 204l8

